[LoopDataPrefetch] Make it testable with opt

[anemet]

Summary

Since this is an IR pass it's nice to be able to write tests without
llc. This is the counterpart of the llc test under
CodeGen/PowerPC/loop-data-prefetch.ll.

[hfinkel]

LGTM

Not specifically related to this pass, but as a general note, we should hook this up to -fprefetch-loop-arrays in Clang (name taken from gcc)/

[anemet]

In D17464#357609, @hfinkel wrote:

Not specifically related to this pass, but as a general note, we should hook this up to -fprefetch-loop-arrays in Clang (name taken from gcc)/

Ah, good point.

include/llvm/InitializePasses.h

 void initializeLintPass(PassRegistry&);
 void initializeLiveDebugVariablesPass(PassRegistry&);
 void initializeLiveIntervalsPass(PassRegistry&);
 void initializeLiveRegMatrixPass(PassRegistry&);
 void initializeLiveStacksPass(PassRegistry&);
 void initializeLiveVariablesPass(PassRegistry&);
 void initializeLoaderPassPass(PassRegistry&);
 void initializeLocalStackSlotPassPass(PassRegistry&);
+void initializeLoopDataPrefetchPass(PassRegistry&);
 void initializeLoopDeletionPass(PassRegistry&);
 void initializeLoopExtractorPass(PassRegistry&);
 void initializeLoopInfoWrapperPassPass(PassRegistry&);
 void initializeLoopInterchangePass(PassRegistry &);
 void initializeLoopInstSimplifyPass(PassRegistry&);
 void initializeLoopRotatePass(PassRegistry&);
 void initializeLoopSimplifyPass(PassRegistry&);
 void initializeLoopSimplifyCFGPass(PassRegistry&);

lib/Transforms/Scalar/Scalar.cpp

void llvm::initializeScalarOpts(PassRegistry &Registry) {
   initializeDSEPass(Registry);
   initializeGVNPass(Registry);
   initializeEarlyCSELegacyPassPass(Registry);
   initializeFlattenCFGPassPass(Registry);
   initializeInductiveRangeCheckEliminationPass(Registry);
   initializeIndVarSimplifyPass(Registry);
   initializeJumpThreadingPass(Registry);
   initializeLICMPass(Registry);
+  initializeLoopDataPrefetchPass(Registry);
   initializeLoopDeletionPass(Registry);
   initializeLoopAccessAnalysisPass(Registry);
   initializeLoopInstSimplifyPass(Registry);
   initializeLoopInterchangePass(Registry);
   initializeLoopRotatePass(Registry);
   initializeLoopStrengthReducePass(Registry);
   initializeLoopRerollPass(Registry);
   initializeLoopUnrollPass(Registry);

test/Transforms/LoopDataPrefetch/basic.ll

+; RUN: opt -mcpu=a2 -loop-data-prefetch -S < %s | FileCheck %s
+target datalayout = "E-m:e-i64:64-n32:64"
+target triple = "powerpc64-bgq-linux"
+
+; Function Attrs: nounwind
+define void @foo(double* nocapture %a, double* nocapture readonly %b) {
+entry:
+  br label %for.body
+
+; CHECK: for.body:
+for.body:                                         ; preds = %for.body, %entry
+  %indvars.iv = phi i64 [ 0, %entry ], [ %indvars.iv.next, %for.body ]
+  %arrayidx = getelementptr inbounds double, double* %b, i64 %indvars.iv
+; CHECK: call void @llvm.prefetch
+  %0 = load double, double* %arrayidx, align 8
+  %add = fadd double %0, 1.000000e+00
+  %arrayidx2 = getelementptr inbounds double, double* %a, i64 %indvars.iv
+  store double %add, double* %arrayidx2, align 8
+  %indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
+  %exitcond = icmp eq i64 %indvars.iv.next, 1600
+  br i1 %exitcond, label %for.end, label %for.body
+
+; CHECK: for.end:
+for.end:                                          ; preds = %for.body
+  ret void
+}